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Unnamed sources tell The Wall Street Journal that the FBI is investigating a cyberattack that targeted the computers of retired Adm. Mike Mullen, the former chairman of the Joint Chiefs of Staff. The hackers are believed to be located outside the U.S., possibly in China.

According to The Wall Street Journal's Devlin Barrett, Julian E. Barnes and Evan Perez, "The hackers targeted Mr. Mullen's personal computers, which he used while working on the grounds of the U.S. Naval Academy since his retirement in 2011, according to officials and others familiar with the probe. Those people said FBI agents took away two computers in late October and returned them in mid-November. One official said that evidence gathered by the FBI points to China as the origin of the hacking, and that it appeared the perpetrators were able to access a personal email account of Mr. Mullen. The official declined to be more specific."

Time's Susan Katz Keating cited a statement from Mullen's office, which read, "Admiral Mullen, now a private citizen, has responded to very specific requests and is cooperating with an ongoing cyber investigation he has been informed is focused overseas."

NBCNews reported, "...Current and former U.S. cyber security officials say the Mullen case is the most recent example of a series of undisclosed hacker attacks on the computer files of former senior U.S. officials. Hackers view their computers as an easier way to get access to sensitive information, said these people, who declined to name the targeted former officials."

Khurram Aziz with Mobile & Apps added, "Mullen was one of five people named to a State Department board last month to review the events surrounding the attack on the U.S. consulate in Benghazi, Libya in September. Mullen also serves on advisory boards at the State Department and Central Intelligence Agency and has access to classified information."